Embodiments of the present disclosure relate to the field of display technology, and in particular, to a mask, a motherboard, a device and method for manufacturing the mask, and a system for evaporating a display substrate.
An organic light emitting diode (OLED) display panel is a panel that uses OLEDs as display pixels. Compared to a traditional liquid crystal panel, an OLED itself emits light rather than using a backlight source. The principle of light emission from OLED utilizes the phenomenon that organic semiconductor material and luminescent material are driven by an electric field to emit light through carrier injection and recombination. Specifically, in an OLED, an indium tin oxide (ITO) transparent electrode and a metal electrode are usually used as an anode and a cathode of the OLED, respectively. Driven by a certain voltage, electrons and holes are injected from the cathode and the anode respectively into an electron transport layer and a hole transport layer. Electrons and holes migrate through the electron transport layer and the hole transport layer respectively to a light-emitting layer and meet each other in the light-emitting layer to form excitons. The excitons excite luminescent molecules which emit visible light through radiative relaxation.
OLED display panels can be mainly divided into passive matrix (PM) type and active matrix (AM) type. In a PM type panel, cathodes and anodes form a matrix and OLED pixels are lighted in a scanning manner. In an AM type panel, a complete cathode layer is usually provided, and an array of thin film transistors (TFTs) is overlaid on an anode layer to determine which pixels emit light and thus determine the composition of an image.
For both types of panels described above, OLED light emitting devices are manufactured by evaporating organic material onto a substrate (e.g., a TFT substrate in an AM type panel). The evaporation of organic material usually requires the use of a mask such as a fine metal mask (FMM). The mask is usually welded onto a metal frame and placed in an evaporator when in use. The component formed by welding the mask and the metal frame together is usually referred to as a mask frame assembly (MFA). Since the mask has a significant influence on the display performance of an OLED light-emitting layer obtained by evaporation, there is a need to continuously improve the performance of the mask.